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Coral/Transcript
Transcript Text reads: The Mysteries of Life with Tim and Moby A boy, Tim, and a robot, Moby, are underwater observing coral. Tim is wearing a diver's suit. Moby is touching a coral reef and asked Tim not to touch the coral. Tim reads from a typed letter. TIM: Dear Tim and Moby, can you tell me all about coral and coral reefs? From, Ricky. TIM: Coral is basically a round, hollow animal with a mouth in the middle. An animation shows coral. MOBY: Beep. TIM: I know it doesn't look much like an animal, but trust me on this. Coral are sessile, which means they don't move around. Instead, they're attached to a hard surface, like a rock, or a shipwreck, or even the skeleton of other corals. The animal is called a polyp. An animation shows a polyp in the ocean. TIM: It's part of the phylum Cnidaria, the same group as jellyfish. An image shows Cnidarian phylum as part of the animal kingdom. A jellyfish represents this branch. TIM: Like jellyfish, polyps have radial symmetry, no head, tentacles around the mouth, and tiny stinging cells called nematocysts. Side-by-side animations show the similarities of jellyfish and polyps. A close-up image shows nematocysts. TIM: The tentacles protect the polyp and help guide food into its mouth, which also excretes waste. MOBY: Beep. TIM: Yeah, I know, it's kind of gross. Coral polyps range from a couple millimeters long to almost thirty centimeters. The larger corals are often solitary. An image shows a large coral. TIM: The smaller ones tend to be colonial. That means they live in groups. An image illustrates what Tim describes. TIM: Colonial corals often live as part of a larger super-colony called a coral reef. Reefs provide food and shelter to a huge diversity of animals. In fact, about twenty-five percent of all marine life can be found in coral reefs. An animation shows a coral reef with sea creatures swimming in and around it. TIM: That's why we have to be so careful about protecting reefs. They're delicate ecosystems. Even small changes to the water temperature or salt level can destroy them. You'll find corals in oceans all over the world, but most reefs are found in tropical waters. That's because they need warm water to survive. A map shows coral reefs all over the world. TIM: They also need plenty of sunlight, which is why reefs grow closer to the surface in clear water. An animation shows sunlight hitting coral reefs in shallow water. MOBY: Beep. TIM: Well, it's kind of complicated but the types of coral that build reefs have a special kind of algae living inside them. A coral detail shows algae. TIM: These algae photosynthesize sunlight, just like plants, and then pass the energy along to the coral polyps. They also provide the coral with oxygen and carbohydrates. The polyp returns carbon dioxide to the algae. Bottom and top animations show sunlight hitting water. The bottom image expands to a fullscreen animation that illustrates what Tim describes. TIM: Polyps use calcium in the seawater to build a protective skeleton. As other polyps grow on top of it, a reef slowly forms. An animation shows part of a coral reef growing. TIM: The corals that build external skeletons are called hard corals. Soft corals have internal fleshy skeletons that make them more flexible than hard. A side-by-side animation shows hard corals and soft corals. TIM: Coral colonies can grow between one and ten centimeters a year. MOBY: Beep. TIM: Well, they can reproduce either sexually, by releasing eggs and sperm into the water, or asexually, by budding or splitting. And sometimes the same coral will do both. An image shows a new coral growing out of an existing coral as it ejects an egg from its mouth. TIM: Although scientists don't know very much about the life cycle of corals, they do know that coral colonies can live from decades to centuries. The Great Barrier Reef in Australia began to form more than eighteen thousand years ago. An animation shows the Great Barrier Reef. TIM: I still don't know how you got down here. Aren't you afraid of rust? Moby frowns and sinks down into the ocean floor. MOBY: Beep. Tim sighs. TIM: I'll go get the lifeguard. Again. Category:BrainPOP Transcripts Category:BrainPOP Science Transcripts